The present invention relates to a technique effective if applied to a gain programmable signal amplifier circuit, a received signal amplifier circuit employed in a wireless communication system and a receiving circuit which down-converts a high frequency received signal into a signal lying in an audio frequency band on a direct conversion system basis, and to, for example, a technique effective suitable for application to a high frequency semiconductor integrated circuit device (hereinafter called high frequency IC) incorporating therein programmable gain amplifiers that constitute a wireless communication system, and a wireless communication system with the high frequency semiconductor integrated circuit device built therein.
A high frequency IC having frequency conversion of transmit-receive signals and a modem function has been used for recent cellular phones. A superheterodyne system which temporarily down-converts a received signal to an intermediate frequency signal and down-converts it to a signal lying in an audio frequency band, and a direct conversion system which down-converts a received signal to a signal lying in an audio frequency band are known for the conventional high frequency IC. The high frequency IC of the direct conversion system is configured in such a manner that an LNA (Low Noise Amplifier) amplifies a received signal and thereafter a mixer combines the received signal and a local oscillation signal, followed by being down-converted to a signal lying in an audio frequency band, and a high gain amplifier circuit amplifies the weak received signal to about 1500 times at the maximum and passes it to a baseband LSI which performs its baseband processing.
The high gain amplifier circuit takes a configuration wherein since it amplifies the weak received signal while removing noise and a signal having an unnecessary frequency, low pass filters LPFs and programmable gain amplifiers (hereinafter abbreviated as PGAs) are alternately connected in several stages. Incidentally, since an analog amplifier circuit starting with PGA produces a DC offset due to variations in element, etc., offset cancellation is essential.
As described above, the receiving circuit of the cellular phone using the plurality of PGAs has conventionally been provided with offset correction circuits every PGA in general. The receiving circuit has been configured so as to sequentially carry out offset cancellations in order from the first-stage PGA to the subsequent-stage PGAs. Such offset cancel operations of PGAs have been described in, for example, a patent document 1 (Japanese Unexamined Patent Publication No. 2003-152480).